Directional drilling apparatus

Abstract

In a directional drilling apparatus in which a sensor/transmitter or sonde is located in one section of a drill string and an element of an adjacent section is configured to “steer” the bore drilled in a predetermined lateral direction, a device is provided for automatically ensuring correct registry or alignment of the sensor/transmitter and the steerable element, this device comprising an azimuth member on the section carrying the sensor/transmitter engageable with a reference member of the adjoining section to present, after such engagement, relative rotation of the azimuth member, which is rotatable in the section carrying it, with the sensor/transmitter, but non-rotatably connected with the sonde. The reference member or the azimuth member is resiliently displaceable axially to allow the two sections to be screwed up together.

1 . In drilling apparatus comprising a series of elongate sections releasably interconnected end to end by interengaging screw threads, orienting means for ensuring that a first component carried by a first and said section adopts a predetermined orientation with respect to a second component carried by, or forming part of, an adjoining section said section when the first and second section are screwed together, wherein said first component is rotatable with respect to said first section and wherein the first section carries a member herein referred to for convenience as an azimuth member, which is rotatable with respect to said first section but is non-rotatable with respect to said first component, and wherein the second section carries a reference member which is fixed against rotation relative to said second component and is engageable with said azimuth member in a predetermined angular orientation relative to the azimuth member as said first and second sections are screwed together end to end, and wherein, when so engaged relative rotation about the axis of said sections, between said azimuth member and said reference member is precluded by such engagement, and wherein one of said azimuth member and said reference member is resiliently displaceable away from the other as said first and second section are screwed together, whereby during an initial phase of screwing said first and second sections together the resiliently displaced member can be displaced axially, to counteract the progressive approach of said first and second sections, as the latter are screwed together, whilst rotating relative to the other said member, until said predetermined angular orientation of the reference member with respect to the azimuth member is reached, allowing the azimuth member and reference member to engage and thereby prevent further relative rotation between the two, whereby the azimuth member, and said first member coupled thereto, will maintain said predetermined orientation relative to said second component despite further rotational movement between said first and second sections during completion of the screwing together of said first and second sections.  
     
     
         2 . A drilling apparatus according to  claim 1  wherein said azimuth member is subject to frictional resistance to such rotation with respect to said first member.  
     
     
         3 . A drilling apparatus according to  claim 2  wherein one of said azimuth member and said reference member has a spigot capable of fitting freely within a complementary socket carried by the other of said members, said spigot and socket being co-axial with the screw connections between said sections, and said spigot or said socket has a lateral projection adapted to slide longitudinally into a longitudinal groove in said socket or said spigot respectively.  
     
     
         4 . Drilling apparatus according to any of  claims 1  to  3  wherein said first component is a sonde and said first section is a sonde section housing said sonde, and wherein said second component is a directional drilling device, the sonde being mounted in the sonde section for sensing its own orientation relative to the vertical or some other external reference and transmitting corresponding data to a receiver spaced from the drill string, and wherein said orienting means is provided for establishing a predetermined angular relationship between the directional drilling device and the sonde.  
     
     
         5 . Drilling apparatus according to  claim 4  wherein the sonde is mounted in the drill string via a resilient suspension arrangement to isolate the sonde from mechanical shocks.  
     
     
         6 . Drilling apparatus according to  claim 5  wherein said suspension arrangement includes fluid or frictional damping means.  
     
     
         7 . Drilling apparatus including a drill string terminating in a drill chuck and a drill bit detachably fitted in the drill chuck, the drill bit having a shank received in the drill chuck, the drill bit shank having a first splined region adjacent a head position of the drill bit and having splines cooperating with grooves between splines of an internally splined complementary portion of said chuck wherein the drill bit has a second splined region adjacent its rear end and has a spline-free band located between said first and second splined regions, and the apparatus includes a liner, adjoining the chuck and having an internal axial passage which is splined in correspondence with the second splined region, over an axial extent less than that of said spline-free band, the axial passage in said liner having, immediately behind the splined region of the liner, a region which is free of splines and has an internal diameter greater than the external diameter of the second splined region of the drill bit shank, said liner being rotatable between an angular position in which the splines thereon are in axial alignment with those in the second splined region of the chuck and an angular position in which they are out of such alignment, whereby the drill shank can be inserted in the passages of complementary cross section in the chuck and the liner, with the splines of the chuck and liner aligned with the corresponding splines of the drill bit shank, until said second splined region of the drill bit shank is within the splineless region of the liner and the end splined region of the liner is within the spline-free band of the drill bit shank, and the liner thereafter rotated so as to move its splines out of axial alignment with those of said second splined region of the drill shank, thereby preventing axial removal of the drill bit.  
     
     
         8 . A percussion drilling bit operable when accorded only a limited range of angular movement about a longitudinal axis of the bit, and wherein the bit comprises cutting tips or inserts arranged in a series of rings or tiers concentric with said longitudinal axis, such that for a predetermined angle of rotation of the bit about said axis, the zone of action of each cutting tip or insert in each said ring or tier overlaps that of at least the adjoining cutting tips or inserts in the same ring or tier.  
     
     
         9 . A percussion drilling bit according to  claim 8  wherein in each said ring or tier, the cutting tips or inserts are displaced angularly about said axis relative to the adjoining cutting tips or inserts in the adjacent rings or tiers.  
     
     
         10 . A percussion drilling bit according to  claim 9  wherein the bit has a face region providing the operative end of the bit, and has a flank region extending rearwardly, i.e. upwardly, away from said face region and towards the remainder of the drilling apparatus, and wherein at least some of said cutting tips or inserts are provided on said flank region.  
     
     
         11 . A bit according to  claim 10  wherein said flank region is waisted and some of said cutting tips or inserts are disposed on the forwardly or downwardly facing surfaces of the groove or valley defined by the waist.  
     
     
         12 . A bit according to  claim 11  wherein the bit has a port for the discharge of a gas or liquid from the interior of the bit, said port being disposed in said waisted region so as to be radially inward of the radially outermost extent of the portions of the bit forward of, or below, said waist.